As a signal transmission system for transmitting audio and/or video data (hereinafter simply referred to as AV data) of a digital format between apparatuses used for video editing etc., a serial digital interface (SDI) system has been used. The signal format of the SDI system has been standardized as SMPTE-295M of the SMPTE (Society of Motion Picture and Television Engineers) as a standard of video signals and audio signals of a digital format.
The SDI system is used in the transmission of the AV data of a digital format of the D1 system, that is, a component video format, and D2 system, that is, a composite video system. The transmission speed thereof is as high as 270 MHz.
In the SDI system, however, the limitation is set that the signal which can be transmitted is only one channel's worth of noncompressed AV data and only eight channels' worth of the audio signal of the base band. At the present time, the SDI system is not necessarily suitable for meeting the demands for multi-media or multi-channels which are now being raised in the field of broadcasting or video editing.
Therefore, recently an SDDI (serial digital data interface) system has been proposed by the Sony Corporation which can transmit a plurality of series of noncompressed AV data, AV data compressed by inter-frame predictive encoding, etc. or computer data and can use the transmission equipment of the conventionally used SDI system to transmit the data.
In a television broadcasting station etc., video equipment such as VTRs and video editing devices used for the editing of videos are connected by a router device etc. AV data of the SDDI system transmitted from any apparatus can be input to any other apparatus via the router device.
In a system in which a large number of video equipment are connected via such a router device (AV server system), there are cases where it is desirable to perform variable speed reproduction changing the speed of reproduction of the AV data at the time of reproduction.
Where such variable speed reproduction is carried out, it is necessary to transmit data indicating the method of reproduction of the AV data from the transmission side of the AV data to the reception side.
For example, where it is intended to make the video equipment on the reception side perform variable speed reproduction for compressed AV data, it is necessary to transfer from the video equipment on the transmission side to the video equipment on the reception side control data concerning the writing control at the time of writing of the AV data after the compressed AV data is subjected to expansion and decoding in the frame memory and concerning the reading control at the time of reading the stored AV data from the frame memory.
However, when the reproduction data indicating the method of reproducing the transmitted AV data such as the transmission data, for example, the AV data, the control data concerning the frame memory, etc. are separately transmitted, there arises a problem in that different equipment become necessary for the transmission of the transmission data and the reproduction data.
Also, when the transmission data and the reproduction data are transmitted via different equipment, there arises a problem that it becomes difficult to establish synchronization between the transmission data and the reproduction data.